Femtosecond Laser-Induced Underwater Superoleophobic Surfaces with Reversible pH-Responsive Wettability

摘要

Wettability-switchable surfaces have become a research hotspot because they can exhibit different superwetting states. In this paper, the copper surfaces with pH-responsive underwater-oil wettability were prepared by femtosecond laser treatment and subsequent chemical modification. The resultant surfaces showed underwater superoleophobicity in alkaline solutions but quasi-superoleophilicity in acidic solutions. The contact angles of an underwater-oil droplet on the resultant surfaces could be reversibly tuned between 157 degrees and 12 degrees by changing the pH of aqueous solutions. Such switchable wettability is ascribed to the modification of the alkyl and carboxylic acids groups on the laser-structured surfaces. The as-prepared surfaces have both oil-resistance and oil-collection abilities by selectively showing underwater superoleophobicity and superoleophilicity. The smart surfaces with pH-responsive oil wettability will have important applications in controlling the oil behavior in water.